Sig Sauer M400 SDI-X 5.56 NATO 30+1 16" Black Threaded Barrel, Moss Green Cerakote Picatinny Rail Aluminum Receiver, M-LOK Handguard, 6 Position Magpul SL Black Synthetic Stock, Reduced Angle Grip, Ambidextrous The M400-SDI X was designed to meet the highest standards of performance and reliability. From the rifle's full suite of ambidextrous controls to its proven mid-length gas system. Features fully Ambi Controls- safety, charging handle, bolt Catch & mag release; 2-Stage Matchlite Duo trigger; free floating M-LOK; mid-length direct impingement operating system and 6 position Magpul SL stock.